The present invention relates generally to automatic door controls and, in particular, to a method and an apparatus for optimizing the performance of individual automatic sliding door systems for elevators.
Automatic sliding doors, for example of the type used in high performance elevators, must meet various operating regulations. Thus, for example, to protect against wedging, it is required that the maximum movement energy of all parts connected together mechanically may not exceed a preset maximum value (for example 10 joules) at a mean closing speed. This requirement sets an upper limit value for the mean closing speed. On the other hand, short door closing times are a prerequisite for good transport performance in high performance elevators. One is therefore forced to fully utilize the greatest possible closing speed which is still permissible while safeguarding for wedging protection and set the door drive thereto. In order to do so, however, it is necessary to know the maximum permissible closing speed.
In the case of an automatic sliding door, the maximum closing speed (vmax) is determined by the movement energy (Ekmax), which is the maximum permissible in terms of safety techniques, and the dynamic door mass (md). The equation is vmax=2.multidot.Ekmax/md. Since Ekmax is preset by the safety regulations, the computation of vmax must be used to determine the dynamic door mass (md). All movable interconnected masses of the door system related to the translational movement of the door leaf to prevent wedging are considered. Belonging to this group of masses are all door leaves, coupling elements and entraining elements, movable door monitoring devices, closing weights, cable connections to the door leaves, door leaf transmissions and so forth. In that case, door fields, which move at half speeds, for example in the case of telescopic doors, have only a quarter of their static mass added into the dynamic mass. Thus, the computation is complicated and difficult and there is a requirement for a simple and exact method to be used to ascertain the dynamic mass (md) for elevator doors.
Different methods have been used to determine the dynamic mass. A first method consists of ascertaining the static masses for the individual door leaves using a weighing machine and converting the same into dynamic masses in correspondence with the drive transmissions. Additionally, a certain value for the dynamic mass of the drive system is added thereto. The result is stored permanently in the electronic door drive system. In a second method, a special mass system is used, which is incorporated in each door system and ascertains the dynamic door masses automatically. A further method examines the system behavior of door systems for different known dynamic door masses. The results are stored in the door drive software and the dynamic door masses of any desired door systems are ascertained therefrom.
All these methods have the disadvantage that they require complicated and expensive equipment and are moreover sensitive to outside interferences as well as being inaccurate.
On the other hand, a method and an apparatus are shown in the Swiss CH patent document 339 775 for measuring the loading torque in the case of electrical drives, in particular in conveying drives. This method sets the drive motor at zero torque for at least a short time in an operating instant provided for the measurement. The acceleration or retardation which appears at the drive machine in this operating state is a direct measure of the loading torque engaging the drive machine. For ascertaining the acceleration or retardation, the speed of the drive machine is measured at the beginning and at the end of a predetermined time interval, and both the of the measurement values are stored in a memory and the difference of both the measurement values is indicated in a display device. This method consists substantially of letting the electrical drive traverse a test section without driving and measuring the arising acceleration or retardation. The equipment for performing this method consists of the combination of a device for switching the motor torque off and a device for measuring the acceleration or retardation. The device for switching the motor torque off is constructed as a relay for the interruption of the electrical power feed to the drive machine, while the device for measuring the acceleration or retardation comprises a pulse generator which is coupled with the drive machine and generates pulses at a repetition frequency proportional to its rotational speed.
The basic disadvantage of this method is in that the loading torque cannot be ascertained absolutely, but only by a proportionality constant. The aforementioned course of movement over a test section leads to an equation K=md.multidot.a with the measured acceleration (a) known and the force (K) as well as the dynamic mass (md) unknown. In order to determine both of the unknowns K and md, a second independent equation from a second test run would be required. The safety requirement however does not provide for making two such test runs each independent of the other in order that both of the corresponding equations are likewise independent and can be solved for both of the unknowns K and md. It also has proved to be disadvantageous that the measured acceleration or retardation (a) represents only "a measure" for the sought loading torque at the drive machine and therefore can be ascertained only inaccurately. Its use, for example for the control of the onset of braking or the braking torque, is therefore limited by the accuracy. This is the case particularly for drives for elevators of lightweight construction, since the dynamic mass (md) serving as the proportionality constant is in this case determined to an increased degree by the load to be conveyed and therefore not only unknown, but also rapidly variable. Furthermore, a basic defect is that the frictional force present in an electrical drive is a part of the loading torque to be ascertained and cannot be ascertained separately. This makes the numerical ascertaining of actually present frictional conditions impossible and thereby precludes their monitoring for precautionary maintenance as well as their comparison for quality assurance.